1. Field of the Invention
The present invention is concerned with a method for the improvement of the technical efficiency and of the quality of tinned mushrooms, by means of blocking enzymatic oxidations before cooking.
2. Discussion of the Art
According to earlier technique, the mushrooms are generally subjected, before the sterilization procedure, to a blanching process that is intended to serve the following purposes:
to deaerate the mushrooms so as to prevent their oxidation, the bulging of the tins, and the appearance of "hobnails" when they are refrigerated;
to reduce the volume of the mushrooms, in such a way that such a quantity may be placed in the tins or jars that, after the process of sterilization, there will be the exact legal net drained weight, and
to tenderize the texture of the mushrooms, so as to prevent any difficulties when filling the containers, such as the breakage of mushrooms or yet accidents at the time of the closing of the tins.
But, that classical technique of blanching the mushrooms entails a certain number of important disadvantages:
(a) During the course of this operation of blanching in water or in a flow of steam, the mushrooms may lose up to 45% of their dry weight; that explains a mediocre technical efficiency and a considerable loss of taste. The tinning experts know, moreover, that the so-called braising is more efficient technically and qualitatively, but constitutes a constricting bottle-neck during production. Moreover, that technique oxidizes the mushrooms much too much; they will, then, present an excessively deep coloring.
(b) In addition, blanching is an operation requiring much thermal energy.
(c) Blanching is a source of pollution. As a matter of fact, the main part of the biological oxygen requirement (B.O.R.) of a mushroom packing house is frequently linked with blanching, in particular with the fact that proteins or starch are liberated.
(d) The process of blanching is often accompanied by the use of chemical products that are tolerated only with difficulty or about to be prohibited by various national authorities.
In the earlier technique, there have already been suggested a certain number of methods that make it possible to avoid the practice of blanching. But, none of those methods makes it possible to bring about, at the same time, all the effects of a blanching process; in addition, these methods must always be accompanied by other treatments. One single treatment in vacuo makes it possible, e.g., to deaerate the mushrooms, but far from reducing their volume, this treatment has a tendency to increase it. For that reason, the required weight to obtain a sufficient net drained weight after sterilization cannot be contained in the receptacle.